The headliner used in motor vehicle passenger compartments is a multi-purpose component in that it serves to present an aesthetically pleasing finished appearance to the ceiling of the passenger compartment and also provides both sound absorption and heat insulation. In recent years, a large amount of emphasis has been placed on the acoustic properties of the headliner because of customer requirements for a quiet environment. And various headliner constructions have been proposed that seek to provide better sound deadening properties while meeting the other demanding requirements of a headliner.
There are primarily two basic types of headliner constructions that are used in the automotive industry; namely, the foam core type and the fibrous core type. The foam core type is the most widely used and typically comprises a normally flexible sound absorbing polyurethane foam core sandwiched between two fiberglass reinforcement layers and surfaced with a thin flexible foam cushioning layer, and a fabric surface layer or cover. In a lesser used version of this type, a rigid foam core is utilized. In the fibrous type headliner, a batting of glass fibers is impregnated with a thermoset resin. The resin impregnated batting is compression molded to the desired contour, and the resin is cured to bond the fibers together to maintain the molded shape. A thin layer of foam, such as polyurethane, normally overlies the molded fiberglass batting, and a fabric cover is attached to the foam for visual appearance. Another fiber type is one formed of polyethylene terephthalate (PET) fibers impregnated with thermoplastic and surrounded on opposite sides with glass fiber reinforcements which are held in place with a thermoset binder. Both the foam core and fibrous core type headliners provide good acoustical insulation with the fibrous type possessing an acoustical advantage but they are also very brittle and as a result are easily fractured or broken during shipment from their site of manufacture to the vehicle assembly plant. Furthermore, they are also subject to breakage or damage such as permanent creasing where they have to be bent or flexed to a significant degree during their installation. As a result, they typically must be installed through a large opening such as the windshield or rear window opening prior to installation of the glass and are not readily replaced at a later date.
An important feature of the above type fiberglass headliners does lie in their self-support but with the accompanying disadvantage of limited elasticity and the problem of the glass fibers irritating assembly plant workers. As a result, a great deal of effort has been directed toward producing a relatively highly elastic, self-supporting type headliner of lightweight construction and particularly one with the acoustical advantage of fibrous sound absorbing material. Many different fibrous type headliner constructions have been proposed that seek to improve the structure thereof in various respects including the above objectives but they typically do not take maximum advantage of the superior acoustical benefits available from the use of the fibrous material and/or add to the complexity of the panel construction. Examples of such proposals are found in the following U.S. Pat. Nos. 4,172,918; 4,330,584; 4,352,522; 4,160,478; 4,480,832; 4,828,910; 4,851,283; 5,068,001; 5,082,716; 5,106,679; 5,258,585; 5,275,865; 5,286,557 and 5,286,929. The above U.S. Pat. No. 4,840,832 is an example of where the panel construction has not been complicated to a great degree with the use of a thermoplastic batting and there is provided a high degree of elasticity but the strength is limited by relying on the integral bonding of the thermoplastic fibers at their random crossing points to provide the main supporting framework structure of the headliner.